List of confirmed characters not from GBA FE:
- Xane (I've got plans for him)
- Aida (no clue what she's called now, Saias's mum)
This isn't an exhaustive list, just a quick list of things so far. No, Marcia's not in, she's definitely pink, not red.
E - did a rough list of more characters in this here https://pastebin.com/7VUPXVcf